Rigid or Flexible
Rigid or Flexible
(OP)
how do i determine if a structure s rigid or flexible?
i know as defined, natural frequency of 1Hz sets the boundary.. but, how do i compute for natural frequency?
would height over length less than 4 be generally assumed as rigid?
would buildings 10 storey or higher be assumed flexible?
would plywood diaphragm mean its flexible?
help much appreciated!
i know as defined, natural frequency of 1Hz sets the boundary.. but, how do i compute for natural frequency?
would height over length less than 4 be generally assumed as rigid?
would buildings 10 storey or higher be assumed flexible?
would plywood diaphragm mean its flexible?
help much appreciated!






RE: Rigid or Flexible
Frequency of 1Hz or less beign flexible is a criterion defined by the ASCE with respect to wind loads. I would not use it as a general rule of thumb per se, but a structure with a natural frequency less than 1 Hz is probably flexible by most standards. In general, the natural frequency of a building will depend on its stiffness and its mass. The damping present in the building will also influence the dynamic response considerably.
Try checking reading some books on structural dynamics. Dynamics of Structures by Chopra is a good text from which to learn.
RE: Rigid or Flexible
RE: Rigid or Flexible
ASCE 07-02
Section 6.2
"Building or other structures, Rigid. A building or other structure whose fundamental frequency is greater than or equal to 1 Hz."
Of course it defines flexible as well.
Rik
RE: Rigid or Flexible
One point is to be away enough from the soil frequency.
Maybe you need the building frequency in as for a servicibility limit state such as comfort and vibration limitations. For that i think you deal with the elements inside in addition to the building as a whole.